I don't know about you, but all of my PC speakers use male 3.5" jacks, thus the thing I posted would be the only necessary component. If for some reason your speakers have female 3.5" slots, then you'd use the other one. I can't say I've ever seen any PC speakers that had female 3.5" connectors on them, though I guess systems with a subwoofer MAY have them on the sub, and use a male-to-male cable to go from PC to speakers, in which case you could use the same cable to go to the Wii plus one of the adapters I posted.
Pretty much any of them will work, you just need to find the way that you'll need the least amount of adapters.
My old setup at our old house was crazy...I had a 3.5" stereo splitter going to a 3.5" extension to a 3.5" to RCA to my stereo, on the other end of the splitter was another 3.5" to RCA going to my VCR input, then from my VCR output was an RCA to 3.5" dongle (not cord) to my line-in and video to my TV-in as well as a video from my graphics card to my VCR (which I used to drive my coaxial TV with)...quite a setup, but complicated and required a ton of adapters...the only downfall of it was that I had to have my PC on if I wanted to listen to games or TV through my stereo.